The goal of Phase II of the NICHD Study of Early Child Care is to extend a collaborative (10-site) prospective, longitudinal study of a cohort of 1247 children and their families, first enrolled at one month of age and studied intensively through age 3 (Phase I). We propose to follow these subjects through first grade in order to investigate: (a) the effects of early alternate care (defined in terms of quality, quantity, type, onset age, and stability) on children's development during the preschool years and the transition to school; (b) the ways in which the effects of early alternate care are moderated by child characteristics and by experiences in the family and in school; and (c) the mediating processes linking early alternate care experiences with later outcomes. The Phase II design involves intensive study of children and their parents at 4-1/2 years and in first grade in their homes, the laboratory, alternate care setting, and school (first grade). Additionally, data will be collected by mailed questionnaires and phone interviews during kindergarten. Child outcome assessments will focus on (a) social-emotional development, including the quality of children's relationships with their parents, friends, and teachers; emotional adjustment, social competence, behavior problems, and self perceptions; (b)cognitive development, including general intellectual functioning, academic achievement, cognitive processes, and language; and (c) health status, including physical growth. Context assessments will focus on (a) the alternate-care environment, including quality, quantity, type, onset age, and stability; (b) the home/family environment, including quality of home life, and parent and structuring characteristics; and (c) school environment, including school climate, curricular features, and the teacher's behavior. We plan to evaluate four models pertaining to the ways in which early alternate-care experiences may affect development: (a) cumulative effects that increase gradually over time or exposure; (b)durable effects of early alternate-care experience that continue even after changes in care; (c) lagged or sleeper effects that are not evident concurrently, but appear at a later point in time; and (d) transient effects of early alternate care that fade over time. Concurrent effects of alternate care also will be examined.